My 29 came fitted with a Simmons Super Power High Compression Cylinder Head.
Whilst not high compression by today’s standards it increased the compression ratio to 6:1. The Ricardo combustion chamber design was licensed from Chrysler.
Sir Harry Ricardo (26 January 1885 – 18 May 1974) was one of the foremost engine designers and researchers in the early years of the development of the internal combustion engine. An exhibition of his work can be found here